| 271. |
- Shi, Feng, et al.
(författare)
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A multi-proxy reconstruction of spatial and temporal variations in Asian summer temperatures over the last millennium
- 2015
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Ingår i: Climatic Change. - : Springer Science and Business Media LLC. - 0165-0009 .- 1573-1480. ; 131:4, s. 663-674
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Tidskriftsartikel (refereegranskat)abstract
- To investigate climate variability in Asia during the last millennium, the spatial and temporal evolution of summer (June–July–August; JJA) temperature in eastern and south-central Asia is reconstructed using multi-proxy records and the regularized expectation maximization (RegEM) algorithm with truncated total least squares (TTLS), under a point-by-point regression (PPR) framework. The temperature index reconstructions show that the late 20th century was the warmest period in Asia over the past millennium. The temperature field reconstructions illustrate that temperatures in central, eastern, and southern China during the 11th and 13th centuries, and in western Asia during the 12th century, were significantly higher than those in other regions, and comparable to levels in the 20th century. Except for the most recent warming, all identified warm events showed distinct regional expressions and none were uniform over the entire reconstruction area. The main finding of the study is that spatial temperature patterns have, on centennial time-scales, varied greatly over the last millennium. Moreover, seven climate model simulations, from the Coupled Model Intercomparison Project Phase 5 (CMIP5), over the same region of Asia, are all consistent with the temperature index reconstruction at the 99 % confidence level. Only spatial temperature patterns extracted as the first empirical orthogonal function (EOF) from the GISS-E2-R and MPI-ESM-P model simulations are significant and consistent with the temperature field reconstruction over the past millennium in Asia at the 90 % confidence level. This indicates that both the reconstruction and the simulations depict the temporal climate variability well over the past millennium. However, the spatial simulation or reconstruction capability of climate variability over the past millennium could be still limited. For reconstruction, some grid points do not pass validation tests and reveal the need for more proxies with high temporal resolution, accurate dating, and sensitive temperature signals, especially in central Asia and before AD 1400.
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| 272. |
- Takeuchi, Fumihiko, et al.
(författare)
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Interethnic analyses of blood pressure loci in populations of East Asian and European descent
- 2018
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Blood pressure (BP) is a major risk factor for cardiovascular disease and more than 200 genetic loci associated with BP are known. Here, we perform a multi-stage genome-wide association study for BP (max N = 289,038) principally in East Asians and meta-analysis in East Asians and Europeans. We report 19 new genetic loci and ancestry-specific BP variants, conforming to a common ancestry-specific variant association model. At 10 unique loci, distinct non-rare ancestry-specific variants colocalize within the same linkage disequilibrium block despite the significantly discordant effects for the proxy shared variants between the ethnic groups. The genome-wide transethnic correlation of causal-variant effect-sizes is 0.898 and 0.851 for systolic and diastolic BP, respectively. Some of the ancestry-specific association signals are also influenced by a selective sweep. Our results provide new evidence for the role of common ancestry-specific variants and natural selection in ethnic differences in complex traits such as BP.
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| 273. |
- Wang, Shuai, et al.
(författare)
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In Situ Synthesis of Tungsten-Doped SnO2 and Graphene Nanocomposites for High-Performance Anode Materials of Lithium-Ion Batteries
- 2017
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 9:20, s. 17163-17171
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Tidskriftsartikel (refereegranskat)abstract
- The composite of tungsten-doped SnO2 and reduced graphene oxide was synthesized through a simple one pot hydrothermal method. According to the structural characterization of the composite, tungsten ions were doped in the unit cells of tin dioxide rather than simply attaching to the surface. Tungsten-doped SnO2 was in situ grown on the surface of graphene sheet to form a three-dimensional conductive network that enhanced the electron transportation and lithium-ion diffusion effectively. The issues of SnO2 agglomeration and volume expansion could be also avoided because the, tungsten-doped SnO2 nanoparticles were homogeneously distributed on a graphene sheet. As a result, the nanocomposite electrodes of tungsten-doped SnO2 and reduced graphene oxide exhibited an excellent long-term cycling performance. The residual capacity was still as high as 1100 mA h g(-1) at 0.1 A g(-1) after 100 cycles. It still remained at 776 mA h g(-1) after 2000 cycles at the current density of lA g(-1).
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| 274. |
- Wang, Yanan, et al.
(författare)
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Gel Polymer Electrolyte with High Li+ Transference Number Enhancing the Cycling Stability of Lithium Anodes
- 2019
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 11:5, s. 5168-5175
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Tidskriftsartikel (refereegranskat)abstract
- Lithium anodes suffer from severe safety problems in liquid electrolyte systems that result from an unstable Li plating/stripping process and Li dendrite growth, leading to rapid degradation of Li metal batteries. A polyethylene (PE)-supported gel polymer electrolyte (GPE) with excellent electrolyte uptake/retention capability was simply prepared in this paper by the construction of cross-linked polymer networks (PNs) on the surface of a poly(ethylenimine)-primed PE separator to stabilize the lithium anode. The highly delocalized negative charge of p-styrene sulfonate groups on PNs plays a role in regulating the Li+ and anion transport, giving rise to a high Li+ transference number. This GPE extended the electrochemical stability to 4.8 V and improved the stability of interface between the electrolyte and lithium metal anode (reduced overpotential and suppressed lithium dendrites) during storage and repeated lithium plating/stripping cycling. The Li metal anode-based battery employing this GPE exhibits excellent cycling stability and C-rate capability.
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| 275. |
- Wu, Yuan, et al.
(författare)
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In situ constructed Ag/C conductive network enhancing the C-rate performance of Si based anode
- 2018
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Ingår i: Journal of Energy Storage. - : ELSEVIER SCIENCE BV. - 2352-152X .- 2352-1538. ; 17, s. 102-108
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Tidskriftsartikel (refereegranskat)abstract
- Poor intrinsic electrical conductivity as well as considerable volume change during lithium alloying/dealloying process has been a critical defect for high theoretical capacity silicon-based anodes. In our work, we demonstrate the synthesis design of multiscale recombined dendritic Si/Ag/C anode for high energy density LIBs via compositing bulky silicon with uniformly distributed Ag NPs, followed by a carbon source PDA (polydopamine) coating step. Here Ag NPs are generated by an in situ redox reaction between Ag+ and PDA, no need for additional reducing agents. According to the characterization analysis, the robust porous Si/Ag/C structure can provide channels for fast Li+ diffusion and electron conduction, promoting the formation of a thinner and more stable SEI film. As a result, the Si/Ag/C composite anode still yields a relatively high residual capacity of 1422.1 mAh g (1) after 100 cycles at 0.2 A g (1). In addition, it remains 633.1 mAh g (1) after 500 cycles at a high current density of 8 A g (1).
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| 276. |
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| 277. |
- Yang, Hui, et al.
(författare)
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Multicriteria evaluation of discharge simulation in Dynamic Global Vegetation Models
- 2015
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Ingår i: Journal of Geophysical Research: Atmospheres. - : Wiley-Blackwell. - 2169-8996. ; 120:15, s. 7488-7505
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we assessed the performance of discharge simulations by coupling the runoff from seven Dynamic Global Vegetation Models (DGVMs; LPJ, ORCHIDEE, Sheffield-DGVM, TRIFFID, LPJ-GUESS, CLM4CN, and OCN) to one river routing model for 16 large river basins. The results show that the seasonal cycle of river discharge is generally modeled well in the low and middle latitudes but not in the high latitudes, where the peak discharge (due to snow and ice melting) is underestimated. For the annual mean discharge, the DGVMs chained with the routing model show an underestimation. Furthermore, the 30year trend of discharge is also underestimated. For the interannual variability of discharge, a skill score based on overlapping of probability density functions (PDFs) suggests that most models correctly reproduce the observed variability (correlation coefficient higher than 0.5; i.e., models account for 50% of observed interannual variability) except for the Lena, Yenisei, Yukon, and the Congo river basins. In addition, we compared the simulated runoff from different simulations where models were forced with either fixed or varying land use. This suggests that both seasonal and annual mean runoff has been little affected by land use change but that the trend itself of runoff is sensitive to land use change. None of the models when considered individually show significantly better performances than any other and in all basins. This suggests that based on current modeling capability, a regional-weighted average of multimodel ensemble projections might be appropriate to reduce the bias in future projection of global river discharge.
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| 278. |
- Zhang, Hao, et al.
(författare)
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A simple method to enhance the lifetime of Ni-rich cathode by using low-temperature dehydratable molecular sieve as water scavenger
- 2019
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Ingår i: Journal of Power Sources. - : ELSEVIER. - 0378-7753 .- 1873-2755. ; 435
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Tidskriftsartikel (refereegranskat)abstract
- Ni-rich cathode materials have received much attention because of their high specific capacity, low cost and environmentally friendly characteristic. However, the nickel-rich cathode is extremely sensitive to moisture, which results in poor structure stability and electrochemical performance. Herein, we demonstrate an efficient and simple route to prolong the lifetime of nickel-rich cathode by introducing a low-temperature dehydratable molecular sieve as water scavenger. The residual water content in electrolyte measurement and nuclear magnetic resonance test manifest that molecular sieve can effectively fix the trace H2O and reduce the decomposition rate of electrolyte from 16.6% to 4.0%, respectively. Transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy confirm that the molecular sieve inhibits the fragmentation of the electrode and the side reactions on the surface of the cathode. This approach improves structural integrity and stabilizes surface structure of the cathode, which increases the capacity retention without sacrificing rate performance. This effective strategy can be extended to other cathode materials which are sensitive to moisture to realize good cycling stability.
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| 279. |
- Zhang, Kaicheng, et al.
(författare)
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SN 2014J in M82 : new insights on the spectral diversity of Type Ia supernovae
- 2018
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 481:1, s. 878-893
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Tidskriftsartikel (refereegranskat)abstract
- We present extensive spectroscopic observations for one of the closest Type Ia supernovae (SNe Ia), SN 2014J discovered in M82, ranging from 10.4 d before to 473.2 d after B-band maximum light. The diffuse interstellar band features detected in a high-resolution spectrum allow an estimate of line-of-sight extinction as A(v) similar to 1.9 +/- 0.6 mag. Spectroscopically, SN 2014J can be put into the high-velocity (HV) subgroup in Wang's classification with a velocity of Si II lambda 6355 at maximum light of upsilon(0) = 1.22 +/- 0.01 x 10(4) km s(-1) but has a low velocity gradient (LVG, following Benetti's classification) of (v) over bar = 41 +/- 2 km s(-1) d(-1), which is inconsistent with the trend that HV SNe Ia generally have larger velocity gradients. We find that the HV SNe Ia with LVGs tend to have relatively stronger Si III (at similar to 4400 angstrom) absorptions in early spectra, larger ratios of S II lambda 5468 to S II lambda 5640, and weaker Si II 5972 absorptions compared to their counterparts with similar velocities but high velocity gradients. This shows that the HV+ LVG subgroup of SNe Ia may have intrinsically higher photospheric temperature, which indicates that their progenitors may experience more complete burning in the explosions relative to the typical HV SNe Ia.
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| 280. |
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